Load lock chamber with gas-sealing bellows

ABSTRACT

A load-lock chamber having a gas-sealing bellows to prevent the flow of gases into the chamber through a shaft opening is disclosed. The load-lock chamber includes a chamber wall that defines a chamber interior. A bellows housing is defined by the chamber wall, and a shaft opening provided in the bellows housing. A flexible bellows is provided in the bellows housing and seals the shaft opening from the chamber interior. A lift shaft having a cassette stage extends through the shaft opening and the bellows and into the chamber interior. A shaft rotation device may engage the lift shaft to rotate the lift shaft and cassette stage in the chamber interior.

FIELD OF THE INVENTION

The present invention relates to process chambers such as etchingchambers used in the etching of material layers on a semiconductor wafersubstrate to fabricate semiconductor integrated circuits on thesubstrate. More particularly, the present invention relates to aload-lock chamber provided with a gas-sealing bellows in a semiconductorsubstrate processing system to reduce or eliminate outgassing andleaking of gas from a lift shaft in the chamber.

BACKGROUND OF THE INVENTION

In the semiconductor production industry, various processing steps areused to fabricate integrated circuits on a semiconductor wafer. Thesesteps include the deposition of layers of different materials includingmetallization layers, passivation layers and insulation layers on thewafer substrate, as well as photoresist stripping and sidewallpassivation polymer layer removal. In modern memory devices, forexample, multiple layers of metal conductors are required for providinga multi-layer metal interconnection structure in defining a circuit onthe wafer. Chemical vapor deposition (CVD) processes are widely used toform layers of materials on a semiconductor wafer. Other processingsteps in the fabrication of the circuits include formation of aphotoresist or other mask such as titanium oxide or silicon oxide, inthe form of the desired metal interconnection pattern, using standardlithographic techniques; subjecting the wafer substrate to a dry etchingprocess to remove the conducting layer from the areas not covered by themask, thereby leaving the metal layer in the form of the masked pattern;removing the mask layer using reactive plasma and chlorine gas, therebyexposing the top surface of the metal interconnect layer; cooling anddrying the wafer substrate by applying water and nitrogen gas to thewafer substrate; and removing or stripping polymer residues from thewafer substrate.

CVD processes include thermal deposition processes, in which a gas isreacted with the heated surface of a semiconductor wafer substrate, aswell as plasma-enhanced CVD processes, in which a gas is subjected toelectromagnetic energy in order to transform the gas into a morereactive plasma. Forming a plasma can lower the temperature required todeposit a layer on the wafer substrate, to increase the rate of layerdeposition, or both. However, in plasma process chambers used to carryout these various CVD processes, materials such as polymers are coatedonto the chamber walls and other interior chamber components andsurfaces during the processes. These polymer coatings frequentlygenerate particles which inadvertently become dislodged from thesurfaces and contaminate the wafers.

The chemical vapor deposition, etching and other processes used in theformation of integrated circuits on the wafer substrate are carried outin multiple process chambers. The process chambers are typicallyarranged in the form of an integrated cluster tool, in which multipleprocess chambers are disposed around a central transfer chamber equippedwith a wafer transport system for transporting the wafers among themultiple process chambers. By eliminating the need to transport thewafers large distances from one chamber to another, cluster toolsfacilitate integration of the multiple process steps and improve wafermanufacturing throughput.

A typical conventional integrated cluster tool is generally indicated byreference numeral 10 in FIG. 1. An integrated cluster tool 10 such as aCentura HP 5200 tool sold by the Applied Materials Corp. of Santa Clara,Calif., includes one or a pair of adjacent load-lock chambers 12, eachof which receives a wafer cassette or holder 13 holding multiplesemiconductor wafers 28. The load-lock chambers 12 are flanked by anorientation chamber 14 and a cooldown chamber 16. Multiple processchambers 18 for carrying out various processes in the fabrication ofintegrated circuits on the wafers 28 are positioned with the orientationchamber 14, the cooldown chamber 16 and the load-lock chambers 12 arounda central transfer chamber 20. A transfer robot 22 in the transferchamber 20 is fitted with a transfer blade 24 which receives andsupports the individual wafers 28 from the wafer cassette or holder 13in the load-lock chamber 12. The transfer robot 22 is capable ofrotating the transfer blade 24 in the clockwise or counterclockwisedirection in the transfer chamber 20, and the transfer blade 24 canextend or retract to facilitate placement and removal of the wafers 28in and from the load lock chambers 12, the orientation chamber 14, thecooldown chamber 16 and the process chambers 18.

In operation, the transfer blade 24 initially removes a wafer 28 fromthe wafer cassette 13 and then inserts the wafer 28 in the orientationchamber 14. The transfer robot 22 then transfers the wafer 28 from theorientation chamber 14 to one or more of the process chambers 18, wherethe wafer 28 is subjected to a chemical vapor deposition or otherprocess. From the process chamber 18, the transfer robot 22 transfersthe wafer 28 to the cooldown chamber 16, and ultimately, back to thewafer cassette or holder 13 in the load-lock chamber 12.

As shown in FIG. 2, each load-lock chamber 12 includes a chamber wall 30defining a chamber interior 32. A cassette stage 34 is mounted on theupper end of a lift shaft 36 which adjusts the height of the cassettestage 34 in the chamber interior 32. The lift shaft 36 extends through ashaft opening 38 provided in the bottom of the load-lock chamber 12.

During operation of the integrated cluster tool 10, a wafer cassette 13is supported on the cassette stage 34. The lift shaft 36 raises andlowers the cassette stage 34 and wafer cassette 13 in the chamberinterior 32, to align wafers 28 (FIG. 1) with a slot (not shown)provided in the chamber wall 30. The transfer blade 24 of the transferrobot 22 extends through the slot to transfer the wafers 28 from andload the wafers 28 onto the wafer cassette 13.

One of the problems which is inherent in operation of the conventionalload-lock chamber 12 is that gases 40 tend to flow into the chamberinterior 32, through the shaft opening 38 and between the lift shaft 36and the chamber wall 30. These gases react with material layers (notshown) deposited on the surfaces of the substrates 28 contained in thecassette 13. Accordingly, a novel load-lock chamber is needed whichprevents the flow of gases into a load-lock chamber, between the liftshaft and the chamber wall, during operation of the load-lock chamber.

An object of the present invention is to provide a novel load-lockchamber having a gas-sealing bellows to prevent gases from entering thebottom of the chamber and reacting with material layers on a substrate.

Another object of the present invention is to provide a novel load-lockchamber having a gas-sealing bellows and a rotating mechanism forrotating or indexing a cassette stage in the chamber.

Still another object of the present invention is to provide a novelload-lock chamber which includes a gas-sealing bellows and a magneticshaft rotation device for rotating or indexing a cassette stage in thechamber.

Yet another object of the present invention is to provide a novelload-lock chamber which may include an elongated bellows cavity forcontaining a gas-sealing bellows; a gas-sealing bellows provided in thebellows cavity for sealing a shaft opening in the bottom of theload-lock chamber; a shaft extending through the shaft opening; a wafercassette stage provided on the shaft; and a magnetic rotation device forrotating a shaft and the wafer cassette stage.

SUMMARY OF THE INVENTION

In accordance with these and other objects and advantages, the presentinvention is generally directed to a novel load-lock chamber having agas-sealing bellows to prevent the flow of gases from outside thechamber interior, into the chamber through a shaft opening in the bottomof the chamber. A lift shaft extends through the shaft opening. Acassette stage is provided on the upper end of the lift shaft, insidethe chamber interior. The invention includes a load-lock chamber havinga chamber wall. A bellows housing having an interior bellows cavityextends downwardly from the bottom of the load-lock chamber. A flexiblebellows contained in the bellows cavity surrounds the lift shaft andseals the shaft opening between the lift shaft and the interior of theload-lock chamber. A shaft rotation device, which may be magnetic,surrounds the lift shaft to rotate and index the cassette stage withrespect to a wafer slot provided in the chamber wall of the load-lockchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a top view of a typical conventional cluster tool used in theprocessing of semiconductor wafers;

FIG. 2 is a schematic of a load-lock chamber of the cluster tool shownin FIG. 1;

FIG. 3 is a schematic of a load-lock chamber with gas-sealing bellows ofthe present invention; and

FIG. 4 is a side view of a bellows and a shaft rotation devicesurrounding a lift shaft of the load-lock chamber shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention has particularly beneficial utility in preventingthe flow of gases from outside a load-lock chamber into the chamberinterior through a shaft opening in the bottom of the chamber. However,the present invention is not so limited in application, and whilereferences may be made to such load-lock chamber, the present inventionis more generally applicable to sealing a shaft opening in processchambers used in a variety of industrial and mechanical applications.

The present invention contemplates a novel load-lock chamber which isprovided with a gas-sealing bellows that blocks the flow of gases fromoutside the chamber, into the chamber interior through a shaft openingin the bottom of the chamber. Consequently, gases are incapable offlowing from outside the chamber, into the chamber interior through theshaft opening. The gases are thus incapable of reacting with materiallayers deposited on the surfaces of semiconductor wafers contained in awafer cassette or holder inside the chamber interior.

The invention typically includes a bellows housing which extendsdownwardly from the load-lock chamber and defines a bellows cavity. Thebellows is contained in the bellows cavity. The invention typicallyfurther includes a shaft rotation device which rotates or indexes acassette stage provided on the upper end of a lift shaft that extendsthrough the shaft opening in the bottom of the load-lock chamber. Theshaft rotation device may be magnetic.

Referring to FIG. 3, an illustrative embodiment of the load-lock chamberof the present invention is generally indicated by reference numeral 42.The load-lock chamber 42 may be a part of an integrated cluster tool inwhich semiconductor wafers are sequentially transferred among multipleprocessing chambers, such as chemical vapor deposition chambers,physical vapor deposition chambers and etching chambers, for example.Typically, such an integrated cluster tool includes a pair of adjacentload-lock chambers, one of which is used to load pre-processed wafersinto the tool and the other to unload the processed wafers from thetool. However, it is understood that the load-lock chamber 42 may beincluded as a part of other systems used in the processing ofsemiconductor wafers.

As shown in FIG. 3, the load-lock chamber 42 includes a chamber wall 44that defines a chamber interior 46. The chamber interior 46 is adaptedto contain a wafer cassette or holder 74, which may be conventional andcontains multiple semiconductor wafers (not shown). A chamber door 45 isprovided in the chamber wall 44 to facilitate opening and closing of thechamber interior 46. An elongated wafer slot 72 is typically provided inthe chamber wall 44 to facilitate the removal of wafers (not shown)from, and/or insertion of wafers into, the cassette 74 in the chamberinterior 46, as hereinafter described.

An elongated bellows housing 48 extends downwardly from the chamber wall44 and defines an interior bellows cavity 50. A housing bottom 49partially closes the bottom of the bellows cavity 50. A shaft opening 52extends through the housing bottom 49 of the bellows housing 48. Anelongated lift shaft 62, the bottom end of which is engaged by a shaftelevation motor 78, extends through the shaft opening 52. A cassettestage 64 is provided on the upper end of the lift shaft 62, inside thechamber interior 46, to support the cassette 74.

An elongated, flexible bellows 54, having multiple folds 54 a, iscontained in the bellows cavity 50. Preferably, the bellows 54 is ametal alloy. Most preferably, the bellows 54 is AM350 stainless steel.However, it is understood that the bellows 54 may be constructed of anyalternative suitable material which is corrosion-resistant.

The bottom end of the bellows 54 is attached to the housing bottom 49 ina fluid-tight seal, according to the knowledge of those skilled in theart. In similar fashion, the upper end of the bellows 54 is attached ina fluid-tight seal to a bellows mount frame 56, which may becylindrical. Accordingly, a bellows interior 55 of the bellows 54 isdisposed in communication with the shaft opening 52, whereas afluid-tight seal is provided between the bellows interior 55 and thechamber interior 46.

Referring to FIG. 4, the bellows mount frame 56 includes acircumferentially-extending flange 56 a to which is mounted a shaftmount plate 58. A plate mount collar 60 is welded, bolted or otherwiseattached to the shaft mount plate 58. The plate mount collar 60 furthermounted on the lift shaft 62, yet permits rotation of the lift shaft 62with respect to the plate mount collar 60. The plate mount collar 60 maybe mounted on the lift shaft 62 by means of an annular flange (notshown) which extends from the plate mount collar 60 and inserts in acircumferential groove (not shown) provided in the exterior surface ofthe lift shaft 62, for example.

A shaft rotation device 66, which may be conventional, is mounted on theshaft mount plate 58. An example of a shaft rotation device 66 which issuitable for the present invention is the magnetic shaft rotation deviceavailable from Trade Mark Electronics (TME), Inc. The shaft rotationdevice 66 typically includes a housing 68 which contains a toroidal orannular housing magnet 70 that is provided around the inner surface ofthe housing 68.

The lift shaft 62 extends through the bellows interior 55 of the bellows54, into the housing 68, and is surrounded by the housing magnet 70,which magnetically rotates the lift shaft 62 in the housing 68, ashereinafter further described. A power supply and controller 76 (FIG. 3)is operably connected to the shaft rotation device 66 to control thepolarity of the housing magnet 70 and selectively rotate the lift shaft62 among multiple positions in the housing 68.

As further shown in FIG. 4, a mount plate 61 may be provided between theupper end of the housing 68 and the shaft mount plate 58 to mount thehousing 68 of the shaft rotation device 66 to the shaft mount plate 58.A shaft bearing 69 is typically provided on the bottom end of thehousing 68. Accordingly, the lift shaft 62 extends through the shaftbearing 69, the housing magnet 70 in the housing 68, the mount plate 61,the shaft mount plate 58 and the plate mount collar 60, respectively.

The shaft bearing 69 centralizes the lift shaft 62 in the housing 68while permitting smooth rotation of the lift shaft 62. Furthermore, theplate mount collar 60 mounts the shaft mount plate 58 and bellow mountframe 56 to the lift shaft 62, such that the bellow mount frame 56 israised and lowered in the chamber interior 46 as the lift shaft 62 israised and lowered by actuation of the shaft elevation motor 78.Simultaneously, the plate mount collar 60, mount plate 61 and shaftbearing 69 permit free rotation of the lift shaft 62 with respect tothose elements.

Referring again to FIG. 3, in operation of the load-lock chamber 42, thechamber door 45 on the load-lock chamber 42 is initially opened toprovide access to the chamber interior 46. Next, a cassette 74, whichcontains multiple semiconductor wafers (not shown) to be processed in amulti-chamber integrated cluster tool (not shown), for example, isplaced on the cassette stage 64, inside the chamber interior 46. Thechamber door 45 is then closed and sealed, and the chamber interior 46is purged with nitrogen or other inert purging gas. Desired chamberpressures may be established in the chamber interior 46, as well.

By actuation of the shaft elevation motor 78, the lift shaft 62 is thenraised in the chamber interior 46 to raise the cassette 74 to the levelof the wafer slot 72 in the chamber wall 44. Simultaneously, theresilient bevel 54 stretches from the compressed configuration shown inFIG. 4 to the expanded configuration of FIG. 3, while maintaining afluid-tight seal between the shaft opening 52 and the chamber interior46. Accordingly, gases flowing into the shaft opening 52 from theexterior of the load-lock chamber 42 accumulate in the bellows interior55 and are thus prevented from entering the chamber interior 46.

Once the cassette 74 has been raised to the level of the wafer slot 72,the cassette 74 can be rotationally positioned or indexed, as necessaryto align the cassette 74 with the wafer slot 72. This facilitates thesubsequent unloading of wafers from the cassette 74, through the waferslot 72, and into a processing chamber (not shown) in the integratedcluster tool, for example, typically by operation of a wafer transferrobot (not shown), as is known by those skilled in the art.

Rotational positioning of the cassette 74 in the chamber interior 46 iscarried out by actuation of the controller 76, wherein the housingmagnet 70 in the housing 68 of the shaft rotation device 66 magneticallyrotates the lift shaft 62, and the cassette stage 64 mounted thereon, inthe selected clockwise or counterclockwise direction. When the cassette74 is sufficiently aligned with the wafer slot 72, rotation of the liftshaft 62 is discontinued and transfer of the wafers from the cassette74, through the wafer slot 72 and into a processing chamber (not shown)is begun.

After the wafers have been sequentially unloaded from the cassette 74,the emptied cassette 74 is removed from the chamber interior 46. This iscarried out typically by lowering the cassette stage 64, opening thechamber door 45, removing the cassette 74 through the door opening, andclosing the chamber door 45. Upon lowering of the lift shaft 62, thebellows 54 partially compresses, thereby expelling gases from thebellows interior 55 and from the bellows housing 48 through the shaftopening 52.

While the preferred embodiments of the invention have been describedabove, it will be recognized and understood that various modificationscan be made in the invention and the appended claims are intended tocover all such modifications which may fall within the spirit and scopeof the invention.

1. A load-lock chamber comprising: a chamber wall defining a chamberinterior; a bellows housing defined by said chamber wall; a shaftopening provided in said bellows housing; a flexible bellows provided insaid bellows housing and sealing said shaft opening from said chamberinterior; and a lift shaft having a cassette stage extending throughsaid shaft opening and said bellows into said chamber interior.
 2. Theload-lock chamber of claim 1 further comprising a shaft rotation deviceoperably engaging said lift shaft for rotating said lift shaft and saidcassette stage in said chamber interior.
 3. The load-lock chamber ofclaim 1 wherein said bellows comprises a metal alloy.
 4. The load-lockchamber of claim 3 further comprising a shaft rotation device operablyengaging said lift shaft for rotating said lift shaft and said cassettestage in said chamber interior.
 5. The load-lock chamber of claim 2wherein said shaft rotation device comprises a housing and a housingmagnet provided in said housing for magnetically rotating said liftshaft.
 6. The load-lock chamber of claim 5 wherein said bellowscomprises a metal alloy.
 7. The load-lock chamber of claim 3 whereinsaid metal alloy comprises stainless steel.
 8. The load-lock chamber ofclaim 7 further comprising a shaft rotation device operably engagingsaid lift shaft for rotating said lift shaft and said cassette stage insaid chamber interior.
 9. The load-lock chamber of claim 8 wherein saidshaft rotation device comprises a housing and a housing magnet providedin said housing for magnetically rotating said lift shaft.
 10. Aload-lock chamber comprising: a chamber wall defining a chamberinterior; a bellows housing defined by said chamber wall; a shaftopening provided in said bellows housing; a lift shaft having a cassettestage extending through said shaft opening and said bellows housing andinto said chamber interior; a bellows mount frame carried by said liftshaft; and a flexible bellows carried by said bellows mount frame insaid bellows housing and sealing said shaft opening from said chamberinterior.
 11. The load-lock chamber of claim 10 further comprising ashaft rotation device operably engaging said lift shaft for rotatingsaid lift shaft and said cassette stage in said chamber interior. 12.The load-lock chamber of claim 10 wherein said bellows comprises a metalalloy.
 13. The load-lock chamber of claim 12 further comprising a shaftrotation device operably engaging said lift shaft for rotating said liftshaft and said cassette stage in said chamber interior.
 14. Theload-lock chamber of claim 11 wherein said shaft rotation devicecomprises a housing and a housing magnet provided in said housing formagnetically rotating said lift shaft.
 15. The load-lock chamber ofclaim 14 wherein said bellows comprises a metal alloy.
 16. The load-lockchamber of claim 15 wherein said metal alloy comprises stainless steel.17. A load-lock chamber comprising: a chamber wall defining a chamberinterior; a bellows housing defined by said chamber wall; a shaftopening provided in said bellows housing; a flexible bellows provided insaid bellows housing and sealing said shaft opening from said chamberinterior; a lift shaft having a cassette stage extending through saidshaft opening and said bellows into said chamber interior; and a shaftrotation device comprising an annular housing magnet surrounding saidlift shaft for rotating said lift shaft and said cassette stage in saidchamber interior.
 18. The load-lock chamber of claim 17 wherein saidbellows comprises a metal alloy.
 19. The load-lock chamber of claim 18wherein said metal alloy comprises stainless steel.
 20. The load-lockchamber of claim 17 further comprising a bellows mount frame carried bysaid lift shaft and wherein said bellows is carried by said bellowsmount frame.